The goal of this remix was to fit the 50mm flat head bolts that I have within the very cool knurled, screw-down stackbox from the original creator. I can jam 25 m8 washers on with a thin nut. 

I have not designed much in the past so this was actually harder than it looked for me! The key was expanding both parts proportionately so that the screw-down mechanism would still function. 

Of note, the photo with two of the stackboxes is this file (the larger) next to the original. 

Hope you enjoy and thanks to the original creator for doing the real work here.